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A system call is a way for a user program to interface with the operating system.
The program requests several services, and the OS responds by invoking a series of
system calls to satisfy the request. A system call can be written in assembly language
or a high-level language like C or Pascal
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In computing, a system call (commonly abbreviated to syscall) is the programmatic way in which a computer program requests a service from the kernel of the operating system on which it is executed.